Dispersion polymerizations offer processing and energy advantages, but would require a new online analysis method for tracking monomer and/or comonomer incorporation into the polymer. Fourier transform near infrared (FTIR) spectroscopy, based on light transmission through the sample, is unable to monitor monomer concentration in presence of two phases due to scattering. There is a need for an on-line monitoring of a two phase polymerization system.
Bandermann et. al., Fourier-Transform Raman Spectroscopic On-Line Monitoring of Anionic Dispersion Block Copolymerization of Styrene and 1,3-Butadiene, Macromol. Rapid Commun, 2001, 22, pp. 690-693, discloses the use of Raman spectroscopy to monitor the anionic dispersion block copolymerization of styrene and 1,3-butadiene.
Santos et al., Online Monitoring of Suspension Polymerization Reactions Using Raman Spectroscopy, Ind. Eng. Chem. Res., 2004, 43, pp. 7282-7289, discloses the use of Raman spectroscopy to monitor aqueous suspension polymerizations.
Additional polymerizations monitored by Raman spectroscopy or other spectroscopy are disclosed in the following references: U.S. Pat. Nos. 6,803,020 and 6,723,804; U.S. Publication Nos. 2003/0130433 and 2004/0176532; International Publication No. WO2004/063234; and Reis et al., Spectroscopic On-Line Monitoring of Reactions in Dispersed Medium: Chemometric Challenges, Analytica Chimica Acta, 595 (2007), pp. 257-265; Vieira et al., Detection of Monomer Droplets in a Polymer Latex by Near-Infrared Spectroscopy, Polymer, 42 (2001), pp. 8901-8906; Jiang et al., Resolution of Two-Way Data from On-Line Fourier—Transform Raman Spectroscopic Monitoring of the Anionic Dispersion Polymerization of Styrene and 1,3-Butadiene by Parallel Vector Analysis (PVA) and Window Factor Analysis (WFA), Chemometrics and Intelligent Laboratory Systems, 70 (2004), pp. 83-92; Witke et al., Ramanspektroskopische Umsatzbestimmung Während der Suspensionspolymerisation von Vinylchlorid, Acta. Polymerica, 34, pp. 627-630 (1983), Abstract; Sears et al., Raman Scattering from Polymerizing Styrene. I. Vibrational Mode Analysis, J. Chem. Phys., 75(4), 1981, pp. 1589-1598; Sears et al., Raman Scattering from Polymerizing Styrene. II. Intensity Changes as a Function of Conversion, J. Chem. Phys., 75(4), 1981, pp. 1599-1602; and Chu et al., Study of Thermal Polymerization of Styrene by Raman Scattering, Macromolecules, 1981, 14, pp. 395-397.
As discussed above, there is a need for on-line process control of a two phase polymerization system. There is a further need for an analytical method that will enable on-line process control, by simultaneously monitoring both the monomer and co-monomer concentrations in both the phases, thus permitting on-line process control. There is a further need for spectroscopy will be used in a non-aqueous, two-phase polymerization process at temperatures up to 200° C., or more, and pressures up to 10 MPa (100 bar). These needs and others have been met by the following invention.